Os alcanos son hidrocarburos, é dicir que teñen só átomos de carbono e .. difiren en enerxía: a conformación alternada é 12,6 kJ/mol menor en enerxía (por . Presentación del tema: “Estructura y Estereoquímica de Alcanos”— . Conformaciones son diferentes arreglos de los átomos producidos al rotar el enlace σ. Análisis conformacional del etano Análisis conformacional del butano Mecánica molecular aplicada a los alcanos y los cicloalcanos

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Estructura y Estereoquímica de Alcanos

Cyclohexanes with tertiary-butyl substituents show that an axial t-butyl group is severely hindered. Cyclohexane can adopt four non-planar conformations: Alkanes with an even number of carbons pack better than those with an fonformaciones number of carbons.

Newman Projections of Butane Caption: Chair Conformation of Cyclohexane Caption: Substituents on a carbon chain are called alkyl groups.

The unfavorable conformation has both methyl groups in axial positions, with a 1,3-diaxial interaction between them. Alcanos con par de C tienen p. Torsional energy of butane.

The more stable conformation has both methyl groups in equatorial positions. They are named by replacing the -ane ending of the alkane with -yl. The Newman Projection of Propane Caption: The equatorial bonds are directed outward, toward the equator of the ring. Two chair conformations are possible for cis-1,3-dimethylcyclohexane.


Among the staggered conformations, the anti is lower in energy because it has the electron clouds of the methyl groups as far apart as possible. The eclipsed conformations are higher in energy than the staggered conformations of butane, especially the totally eclipsed conformation. Some conformations can be more stable than others. Angle strain and torsional strain account for the high reactivity of 4-membered rings.

This kind of interference between two bulky groups is called steric strain or steric hindrance. C5H12 C H 3 2 n-pentano iso-pentano neo-pentano Chapter 3. Alcanos ramificados tienen p. Longer chained alkanes have greater surface area and can have more surface contact and more induced dipoles than branched alkanes with smaller surface areas.

Solution The longest carbon chain contains eight carbon atoms, so this compound is named as an octane. Conformations of Cyclopentane Caption: Conformational Analysis of Ethane Caption: Some common alkyl groups and their names. The molecular formula of alkanes is CnH2n, two hydrogen less than an open chain alkane. The conformation of cyclobutane is slightly folded.

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Ambas conformaciones tienen un metil axial y otro ecuatorial. The angle compression of cyclopropane is The df conformation is about 3. The ring strain of a planar cyclobutane results from two factors: Numbering from left to right gives the first branch on C2; numbering from right to left gives the first branch on C3, so we number from left to right.

All the C-H bonds are staggered in the chair conformation. Ethane, the two-carbon alkane, is composed of two methyl groups with overlapping sp3 hybrid orbitals forming a sigma bond between them. Conformational Analysis of Propane Caption: The simplest alkane is methane, CH4. Conformational energy of cyclohexane. Alcohols are compounds whose molecules have a hydroxyl.


Chair Conformations of cis-1,3-Dimethylcyclohexane Caption: Los botones se encuentran debajo. The chair conformation is most stable, followed by the twist boat.


Chair Conformations of trans-1,3-Dimethylcyclohexane Caption: Same Length Chains Caption: Axial hydrogens are pointed straight up or down, parallel to the axis of the ring. Alkyl substituents on cyclohexane rings will tend to be equatorial to avoid 1,3-diaxial interactions. Nomenclature of Alkyl Groups Caption: Chair interconversion would still produce an axial and an equatorial methyl.

When a bond of propane rotates, the torsional energy varies much like it does in ethane, but with 0. The axial substituent interferes with the axial hydrogens on C3 and C5. Los substituyentes axiales conformacionse con los H axiales del C 3 y C 5.